JPH0417492B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides, for example, high-level data link control.
Control: Hereinafter abbreviated as HDLC. ) procedure to continuously transfer a plurality of pieces of transmission data.

In a data transmission system that continuously transfers data using a conventional HDLC procedure, a plurality of pieces of transmission data are normally output to a line in the order of requests. Therefore, once transmission data is passed to the communication control device, even if urgent transmission data occurs thereafter, it will not be transmitted until the previously passed transmission data has been output to the line.

To deal with this problem, the communication control device is configured so that only one transmission request is accepted at the same time, and the side that passes the transmission data to the communication control device distinguishes between priority data and non-priority data. 1 that was passed earlier by the communication control device.
One possible method is to take out the next data in order of priority and pass it to the communication control device after one piece of data has been output to the line.
The priority data is output to the line by simply waiting for the time for outputting the non-priority data to the line.

However, in such a method, after the communication control device notifies the completion of data output to the line, it waits for the arrival of priority data, so if a certain period of time has not elapsed, the next transmission data is not sent to the communication control device. If a high-speed transmission line is used, the utilization rate of the line will decrease. For example, 48Kbps
If there is a delay of 10ms on a line, the utilization rate will drop by 23%.

An object of the present invention is to provide a data transmission system that outputs priority data to a line with minimum waiting time without reducing line utilization efficiency even in the case of high-speed transmission.

In order to achieve such an objective, the present invention includes first and second memory means for respectively storing high-priority priority data and low-priority non-priority data, and storage means for storing data to be output to a line. The priority data stored in the first memory is continuously output to the third memory up to the first predetermined number, and the non-priority data stored in the second memory is is characterized in that when a predetermined condition is met, data up to a second predetermined number smaller than the first predetermined number is output to a third memory.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows the configuration of an embodiment of a communication control device that implements the data transmission method according to the present invention.
Reference numeral 1 indicates a communication control device composed of a microcomputer, 2 a modem, and 3 a line leading to a partner station. In the communication control device 1, 4 is a data processing section that processes data according to the HDLC procedure, 5 is a data output section that outputs data processed by the data processing section 4 one byte at a time, and 6 is a section that is passed from the data output section 5. 7 is a memory section;
and 9 are channels for transmitting priority data and non-priority data, respectively.

In addition, in the memory section 7, 71 is a channel 8.
a priority data group area for storing priority data from;
72 is a non-priority data group area for storing non-priority data from channel 9; 73 is a priority data group area 7
1, a counter 74 indicating the number of data in the non-priority data group area 72, and 75 an index for notifying the data processing unit 4 whether it is okay to start processing the non-priority data. , 76
is a line output data group area that stores data processed according to the HDLC procedure in the data processing unit 5;
77a is a counter that indicates the number of data in the data group area 76; 77b is a counter that indicates the number of remaining bytes of data being output on the line; 78 is a buffer that receives line output data from the data output unit 5 one byte at a time;
79 is when even one buffer 78 is vacant,
This is an index for permitting the data output unit 5 to output the next 1 byte.

Further, 80 is a register that stores the number of data that can be continuously transmitted (hereinafter referred to as the maximum outstanding frame number) specified in the HDLC procedure;
A counter 81 indicates the number of data that has been continuously transmitted up to now in the HDLC procedure (hereinafter referred to as the number of outstanding frames).

Channels 8 and 9 from the host computer, etc.
Priority data and non-priority data are respectively set in the priority data group area 71 and non-priority data group area 72 of the memory section 7 via the
Add 1 to the contents of counters 73 and 74.

When a transmission permission command is transmitted from the partner station, the data processing section 4 performs the processing shown in the flowchart of FIG.

The processing in the data processing section 4 will be explained with reference to FIG.

First, in step 11, the counter 73 checks whether there is transmission data in the priority data group area 71.
If there is data, that is, counter 7
If the content of 3 is not 0, in step 12,
One piece of data in the area 71 is moved to the line output data group area 76, and the contents of the counter 73 are changed by -1.
Add. In the next step 13, the counter 7
Add 1 to the contents of 7a. Also, in step 14, 1 is added to the outstanding frame number stored in the counter 81, and step 14 is started.
At 15, indicator 75 is turned off. Note that this indicator 75 is turned on at the time of initialization.

Next, in step 16, the outstanding frame number in the counter 81 is changed to the outstanding frame number in the register 8.
It is checked whether it is equal to the maximum outstanding frame number set to 0, and if it is not equal, the process returns to step 11 and the above-described process is repeated. Thereby, the priority data is processed with the limit up to the maximum number of outstanding frames and set in the line output data group area 76.

If it is found in step 11 that there is no priority data, in step 17, the indicator 7
5, it is checked whether non-priority data can be sent. If it is okay, in step 18, it is checked whether the contents of the counter 74 are not 0 and whether there is non-priority data. If it is not 0, one non-priority data in the non-priority data group area 72 is moved to the line output data group area 76 in step 19, -1 is added to the counter 74, and the process moves to step 13. For the remaining non-priority data, the index 75 is the data output unit 5.
When set on as described below by
If there is no priority data, only one is processed and set in the line output data group area 76.

In this way, maximum outstanding
When the number of frames is reached or when the indicator 75 turns on and the contents of the counters 73 and 74 become 0, a command RRF indicating that there is no data to be transmitted (corresponds to CMD2 described later) is executed in step 20.
is set in the line output data group area 76, and at the same time, in step 21, 1 is added to the contents of the counter 77a.

Similarly, when receiving a transmission permission command from the other station, the contents of counters 73 and 74 are 0, that is, when there is neither priority data nor non-priority data, the command indicates that there is no data to be transmitted.
The RRF is set in the line output data group area 76 (step 20).

Next, the processing of the data output section 5 will be explained with reference to the flowchart of FIG.

In step 22, it is checked whether the content of the counter 77b is not 0 and it is checked whether there is data being sent. If there is, in step 23, it is checked whether the indicator 79 is on or not, and 1 byte is sent. Check whether output is possible. If possible, in step 25 one byte of data is extracted from the line output data group area 76 and set in the buffer 78, and in step 26 -1 is added to the contents of the counter 77b. Furthermore, in step 27, the content of the counter 77b becomes 0.
If it is 0, step 28
Then -1 is added to the contents of the counter 77a, and the process moves to steps 29 and 30. Steps 29 and 30
Now, check whether the contents of counters 77a and 77b have become 1 and 10 or less, respectively, that is, whether the number of remaining data in area 76 has become 1 and the number of remaining data has become 10 bytes or less, and if so, In step 31, the indicator 75 is turned on to permit the data processing section 4 to transmit non-priority data. Note that one piece of data is, for example,
It consists of 128, 256 bytes, etc.

If it is determined in step 22 that there is no data being transmitted, then in step 32 the counter 77a is checked to see if the content is 0 to see if there is any data to be transmitted. In step 33, the byte length of the transmission data is set in the counter 77b, and the process proceeds to step 23 described above.

Furthermore, the processing of the line control section 6 will be explained with reference to the flowchart of FIG.

In step 34, it is checked whether there is data to be sent in the buffer 78. If there is, in step 35, 1 byte of data in the buffer 78 is output to the modem 2, and in step 36,
Turn on indicator 79. On the other hand, if there is no sending data in the buffer 78, a flag pattern is output to the modem 2 in step 37.

The flow of data when the above processing steps are executed will be explained with reference to FIG. In addition, in Figure 5,
The horizontal axis shows the time axis.

In the figure, A is the number of data in the non-priority data group area 72 of the memory unit 7, that is, the value of the counter 74 is taken on the vertical axis, and three non-priority data
The case where a ₁ , a ₂ , and a ₃ are received from channel 9 is shown. B indicates the number of data in the priority data group area 71, that is, the value of the counter 73, taken on the vertical axis, and indicates the case where three priority data b ₁ , b ₂ , and b ₃ are received from the channel 8. C is the number of data in the line output data group area 76, that is, the counter 7
The value of 7a is plotted on the vertical axis, and D indicates data being sent to the line.

Now send permission command CMKD1 from the other station.
is sent, at timing _d1 , the priority data b ₁ and b ₂ in the priority data group area 71 are set in the line output data group area 76 and then output to the line. Furthermore, if priority data is stored in the area 71 during the transmission enabled state from receiving the transmission permission command to sending the transmission completion command, the timing
At _d2 , the data is set in area 76 in the same manner.

On the other hand, if there is no priority data to be sent when a transmission permission command is received from the partner station, or if a non-priority data transmission permission signal S is received from the data output unit 5 in a transmission permission state, in the example shown in the figure, the timing is d ₃
In ~ _d5 , only one piece of non-priority data is extracted from the area 72, processed, and then set in the line output data group area 76. As shown in the figure, the non-priority data transmission enable signal S is notified to the data processing unit 4 a certain period of time before all the last data in the line output data group area 76 is output to the line. So,
Even if processing starts from that point, the line will not be idle. Further, even if there is a plurality of non-priority data, the priority data can be output to the line by waiting at most the time required to output one non-priority data to the line.

When the non-priority data transmission enable signal S is transmitted to the data processing unit 4, if there is neither priority data nor non-priority data, a command CMD2 for ending the transmission at timing _d6 is set in the line output data group area 76. .

In the above-described embodiment, the data processing section, the data output section, and the line control section are each configured separately, but they may be integrated into one processing section. Further, in the above-described embodiment, the communication control device is realized by a microcomputer, but the present invention is not limited to this, and the communication control device can also be realized by dedicated hardware.

Furthermore, the present invention is applicable not only to data transmission systems using the HDLG procedure but also to systems that transmit priority and non-priority data in general.

As described above, according to the present invention, if it is priority data, a plurality of pieces of data are outputted to the line in succession, and if it is non-priority data, it is outputted to the line little by little, for example, one piece of data at a time. Data can be output to the line by simply waiting the time required to output at most one non-priority data to the line,
It is possible to provide priority data in advance without reducing line usage efficiency.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of a device implementing the data transmission method according to the present invention, and FIGS. 2, 3, and 4 are the data processing section, data output section, and line control section shown in FIG. 1, respectively. FIG. 5 is a flow chart showing an example of the processing in the device shown in FIG. 1, and FIG. 5 is a time chart showing an example of the data flow in the device shown in FIG. 1... Communication control device, 2... Modem, 3... Line, 4... Data processing section, 5... Data output section,
6... Line control section, 7... Memory section, 8, 9...
Channel.

Claims (1)

[Scope of Claims] 1. A first memory means for storing a plurality of high-priority data (priority data) supplied from a host device, and a first memory means for storing a plurality of low-priority data (priority data) supplied from a host device. a second memory means for storing non-priority data);
first and second counter means for indicating the number of remaining data in the second memory means; a third memory means for storing a plurality of pieces of transmission data to be output to the line; a third counter means for storing the number of remaining data pieces, and a fourth counter means for storing the number of data pieces that can be continuously transmitted; the priority data stored in the first memory means; The non-priority data stored in the second memory means is continuously transferred to the third memory until the first number of consecutively transmittable data indicated by the fourth counter means is reached. When there is no priority data in the first memory means and the number of data in the third memory means indicated by the third counter means is less than or equal to a predetermined number, a second data smaller than the first data number is The data is transferred to the third memory means within the range of the number of data, and when the number of data written to the third memory means reaches the number of consecutively transmittable data indicated by the fourth counter means, the third A data transmission system characterized in that predetermined control data is written in memory means, and the data stored in the third memory means is sequentially output to a line. 2. In the data transmission method described in paragraph 1, the fifth counter means is provided for storing the remaining byte length of the data being transmitted to the line, and the first byte of the transmission data is stored from the third memory means. When read, the number of remaining bytes of the above transmission data is set to the fifth
and reading out the transmission data in byte units from the third memory means;
A data transmission method characterized in that data is transmitted by subtracting the value of the fifth counter each time.